Climate Narrative for Jackson County, North Carolina.
Prepared by the Natural Resources Conservation Service National Water and Climate Center, Portland, Oregon.
Climate Tables are created from climate station Cullowhee, North Carolina.
Thunderstorm days, relative humidity, percent sunshine, and wind information are estimated from First Order station Asheville, North Carolina.
Table 1 gives data on temperature and precipitation for the survey area as recorded at Cullowhee in the period 1961 to 1990. Table 2 shows probable dates of the first freeze in fall and the last freeze in spring. Table 3 provides data on the length of the growing season.
In winter, the average temperature is 38.8 degrees F and the average daily minimum temperature is 26.5 degrees. The lowest temperature on record, which occurred at Cullowhee on January 21, 1985, was -19 degrees. In summer, the average temperature is 71.3 degrees and the average daily maximum temperature is 83.4 degrees. The highest temperature, which occurred at Cullowhee on July 28, 1952, was 99 degrees.
Growing degree days are shown in Table 1. They are equivalent to "heat units". During the month, growing degree days accumulate by the amount that the average temperature each day exceeds a base temperature (50 degrees F). The normal monthly accumulation is used to schedule single or successive plantings of a crop between the last freeze in spring and the first freeze in fall.
The average annual total precipitation is about 51.03 inches. Of this, about 24.60 inches, or 48 percent, usually falls in May through October. The growing season for most crops falls within this period. Precipitation across Jackson county is quite variable depending on elevation and location. The southern portion of the county, particularly at higher elevations, receives as much as 100 inches of precipitation annually, and is one of the wettest spots in the United States east of the Pacific Northwest. The heaviest 1-day rainfall during the period of record was 5.00 inches at Cullowhee on March 27, 1994. Thunderstorms occur on about 45 days each year, and most occur between May and August.
The average seasonal snowfall is 11.8 inches. The greatest snow depth at any one time during the period of record was 19 inches recorded on March 14, 1993. On an average, 3 days per year have at least 1 inch of snow on the ground. The heaviest 1-day snowfall on record was 17.0 inches recorded on March 13, 1993.
The average relative humidity in mid-afternoon is about 58 percent. Humidity is higher at night, and the average at dawn is about 90 percent. The sun shines 58 percent of the time in summer and 57 percent in winter. The prevailing wind is highly dependent on location in this mountainous county. Average wind speed is highest, around 9 miles per hour, in the winter and early spring months.
TABLE 1.--TEMPERATURE AND PRECIPITATION
(Recorded in the period 1961-90 at CULLOWHEE, NC2200)
| |
| Temperature | Precipitation
| | _
| | | | 2 years in | | |2 years in 10| |
Month | | | | 10 will have-- | Average | | will have-- | Average |Average
|Average|Average|Average| Maximum | Minimum |number of|Average| | |number of|snowfall
| daily | daily | |temperature|temperature| growing | | Less | More |days with|
|maximum|minimum| | higher | lower | degree | |than--|than--|0.10 inch|
| | | | than-- | than-- | days* | | | | or more |
| | | | | | | | | | |
| 0F | 0F | 0F | 0F | 0F | Units | In | In | In | | In
| | | | | | | | | | |
January-----| 48.7 | 24.7 | 36.7 | 69 | -4 | 9 | 4.32 | 2.61| 5.86| 8 | 4.2
| | | | | | | | | | |
February----| 52.8 | 27.0 | 39.9 | 72 | 3 | 18 | 4.64 | 2.49| 6.53| 7 | 3.5
| | | | | | | | | | |
March------| 62.0 | 34.1 | 48.0 | 81 | 11 | 79 | 5.43 | 3.32| 7.33| 9 | 1.8
| | | | | | | | | | |
April------| 70.1 | 40.7 | 55.4 | 87 | 22 | 199 | 3.72 | 2.09| 5.17| 6 | 0.0
| | | | | | | | | | |
May------| 76.8 | 49.1 | 62.9 | 88 | 29 | 402 | 4.53 | 2.56| 6.27| 8 | 0.0
| | | | | | | | | | |
June------| 82.2 | 56.4 | 69.3 | 92 | 38 | 578 | 4.44 | 2.29| 6.33| 8 | 0.0
| | | | | | | | | | |
July------| 84.4 | 60.8 | 72.6 | 93 | 48 | 701 | 4.56 | 2.60| 6.30| 8 | 0.0
| | | | | | | | | | |
August------| 83.7 | 60.4 | 72.1 | 92 | 47 | 682 | 4.12 | 2.14| 5.85| 7 | 0.0
| | | | | | | | | | |
September---| 78.6 | 55.1 | 66.8 | 89 | 35 | 505 | 3.62 | 1.70| 5.27| 6 | 0.0
| | | | | | | | | | |
October-----| 70.5 | 42.5 | 56.5 | 85 | 22 | 224 | 3.36 | 1.88| 4.89| 5 | 0.0
| | | | | | | | | | |
November----| 60.8 | 34.4 | 47.6 | 77 | 12 | 72 | 3.84 | 2.65| 4.93| 6 | 0.5
| | | | | | | | | | |
December----| 51.7 | 28.0 | 39.8 | 69 | 3 | 23 | 4.45 | 2.32| 6.31| 7 | 1.8
| | | | | | | | | | |
| | | | | | | | | | |
Yearly: | | | | | | | | | | |
| | | | | | | | | | |
Average---| 68.5 | 42.8 | 55.6 | --- | --- | --- | --- | ---| ---| --- | ---
| | | | | | | | | | |
Extreme---| 98 | -19 | --- | 95 | -6 | --- | --- | ---| ---| --- | ---
| | | | | | | | | | |
Total-----| --- | --- | --- | --- | --- | 3493 | 51.03 | 43.53| 57.96| 85 | 11.8
| | | | | | | | | | |
* A growing degree day is a unit of heat available for plant growth. It can be calculated by adding the maximum and minumum daily temperatures, dividing the sum by 2, and subtracting the temperature below which growth is minimal for the principal crops in the area (50 degrees. F)
TABLE 2.--FREEZE DATES IN SPRING AND FALL
(Recorded in the period 1961-90 at CULLOWHEE, NC2200)
|
| Temperature
|
| _
Probability | | |
| 24 0F | 28 0F | 32 0F
| or lower | or lower | or lower
| | |
| | |
Last freezing | | |
temperature | | |
in spring: | | |
| | |
1 year in 10 | | |
later than-- | April 16 | May 5 | May 19
| | |
2 year in 10 | | |
later than-- | April 10 | April 30 | May 13
| | |
5 year in 10 | | |
later than-- | March 30 | April 20 | May 2
| | |
First freezing | | |
temperature | | |
in fall: | | |
| | |
1 yr in 10 | | |
earlier than-- | October 17| October 5| September 27
| | |
2 yr in 10 | | |
earlier than-- | October 24 | October 11| October 1
| | |
5 yr in 10 | | |
earlier than-- |November 6 | October 22 | October 10
| | |
| | |
TABLE 3.--GROWING SEASON
(Recorded for the period 1961-90 at CULLOWHEE, NC2200)
|
| Daily Minimum Temperature
| During growing season
| _
Probability | | |
| Higher | Higher | Higher
| than | than | than
| 24 0F | 28 0F | 32 0F
| | |
| Days | Days | Days
| | |
9 years in 10 | 194 | 165 | 138
| | |
8 years in 10 | 203 | 171 | 146
| | |
5 years in 10 | 220 | 183 | 160
| | |
2 years in 10 | 238 | 195 | 174
| | |
1 year in 10 | 247 | 202 | 182
| | |